Recently, a light-emitting diode (LED) has been used as a light source of a lighting apparatus. In this light source, a number of LED bare chips are mounted on a substrate, and each LED chip is electrically connected to a wiring pattern by bonding wires. A plurality of such substrates is housed in a main body made of metal such as aluminum (Jpn. Pat. Appln. KOKAI Publication No. 2009-54989).
In such a lighting apparatus, power is usually supplied from a lighting control device connected to commercial power source, and lighting of the LED chip is controlled. The metallic main body is maintained at a ground potential.
However, in the above lighting apparatus, though a power switch (one-position) of the lighting control device is being turned off, an LED chip is accidentally lit dimly. This phenomenon is caused by a noise superimposed on a power line. Stray capacitance is generated between a conductor such as the wiring pattern connected to the LED chips and the metallic main body close to the conductor, and a minute current flows in the LED chip as a leakage current.
Further, when the power switch is turned on, a rush current may flow into LED chips as a noise, and break the LED chips. As well known, an LED is weak to electrostatic breakdown, and is easily broken when subjected to a high voltage caused by a noise such as static electricity. For example, a worker may touch a wiring pattern while assembling a lighting apparatus. In such a case, if the worker's hand is electrostatically charged, an overcurrent is applied to an LED, and damages or breaks the LED. In addition, jigs and tools electrostatically charged during the assembling work discharges electricity, an overcurrent is applied to an LED, and damages or breaks the LED, decreasing the reliability.
To solve the above problems, or to prevent accidental lighting, a capacitor is inserted as a bypass element in parallel to an LED chip. To prevent a damage or breakage of an LED by static electricity, a capacitor or a constant-voltage diode is inserted as a protective element.
These capacitor and constant-voltage diode as anti-noise parts may be mounted on a circuit board of a power supply circuit, or mounted together with an LED on the same substrate.
However, when the capacitor and constant-voltage diode as anti-noise parts are mounted on a circuit board of a power supply circuit, a wiring pattern and land are additionally provided on the circuit board, and the components must be connected to these pattern and land, resulting in a complex structure. Further, when such components are mounted together with LEDs on the same substrate on which the LEDs are mounted as a light-emitting element, the anti-noise parts obstruct the light emitted from the LEDs.